Method of making hollow articles



July 27, 1943. H. HABART ET AL METHOD OF MAKING HOLLOW ARTICLES Filed Aug. 2, 1940 T HE ATTOR Y,

. Patented July 27, 1943 UNITED .STATES PATENT OFFICE' ME'rnon or 2,325,314 MAKING noLLow ARTICLES y Herbert Habart and Harry W. Hudson, l'lllwoodv City, Pa.,.assignors to National Tube Company, -a corporation of New Jersey Application August 2, i540, Serial No. `350,154

1 claim.' (ci. 25a- 156) This invention is concerned with the piercing, of solid stainless-steel billets in a seamless tube piercing-mill when the stee1 contains about 25% chromium and about 20% nickel.

In the manufacture of seamless tubes itis considered preferable to pierce solid billets rather than billets that have been drilled. Prior tothe present inventionlt has been commercially imf present invention. This increase in the mangapossibie te pierce send staimess steel biute' of the above chromium and nickel content because the load placed on the mill during the piercing was more than a mill of standard design could carry.

The accompanying drawing schematically illustrates the present invention, the drawing being legend so that it is unnecessary to make specic 'reference to the various parts by nu. e

merals.

According to the present invention, while the stainless steel is molten its manganese content is adjusted to from more'than 2% to not more than 4% while keeping the other constituents of the steel within the commercial range usual to its 25% chromium and 20% nickel content, the steel being rolled to solid billets when it solidies and these billets being pierced in'a seamless tube.'

piercing mill.l The pierced'billets subsequently may be processed to finished tubes by conven" tional methods, it being possible to produce tubes with relatively thin walls. The characterizing feature is the adjustment of the manganese content, it having beenl found that when the manganese exceeds 2% the load on the piercing mill is materially reduced so that the mill can be commercially operated with safety and without inover a piercing point positioned in the pass ofthe pierce solid billem ypiercing mill as contemplated, herein ons-ists of In the above analysis the manganese content not given since it is increased from usual to from more than 2% to less than 4% in the case of the nese content does not aiect harmfully the stainless or othercharacteristics of the steel. The main eilectjof the manganese appears to be the reduction in 'the load ona piercing mill from a point where the load is too high to be safely 'carried` by a standard mill to one .where it is within safe limits, As a matter of fact, the pierceability of 25-20 stainless with its manganese content adjusted asdescrlbed, is better than that of 1&8 stainless. Q

It is also to be understood that a seamless tube ff diagonal rolls which grip thebillet and work it i said steel is molten to give said steel a manganese corporating any features uncommon to' piercing mills satisfactory for use in piercing stainless steels of lower chromium and nickel content.

It is to be understood that the stainless steel with which the present invention is concerned is commercially known as 25-20 stainless and its usual commercial for seamless tubes is:

Per cent Chromium 24 26 Nickel 19 to21 Carbon maximum-- .20 Phosphorua do .03 Sulphur do.--.. .03 Silicon Iron content oi' from more than 2% to not more than 4% while keeping lthe other constituents of said steel within usual commerciaranges, rolling said prepared' steelto solid billets when it solidii-les and subsequently' piercing said prepared solid billets in a seamless tube piercing n'iill, said manganese content causing a material reduction in the load on said mill during said piercing.

HERBERT HABART. HARRY W. HUDSON.

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